1. Field of the Invention
The present invention relates generally to an apparatus and method for performing a thermotherapy patient treatment protocol. More particularly, the invention relates to a novel apparatus and method for heating the prostate gland for therapeutic purposes.
2. Description of Related Art
Thermotherapy treatment is a relatively new method of treating diseased and/or undesirably enlarged human prostate tissues. Hyperthermia treatment is well known in the art, involving the maintaining of a temperature between about 41.5° through 45° C. Thermotherapy, on the other hand, usually requires energy application to achieve a temperature above 45° C. for the purposes of coagulating the target tissue. Tissue coagulation beneficially changes the density of the tissue. As the tissue shrinks, forms scars and is reabsorbed, the impingement of the enlarged tissues, such as an abnormal prostate, is substantially lessened.
The higher temperatures required by thermotherapy require delivery of larger amounts of energy to the target prostate tissues. At the same time, it is important to shield nontarget tissues from the high thermotherapy temperatures used in the treatment. Providing safe and effective thermotherapy, therefore, requires devices which have further capabilities compared to those which are suitable for hyperthermia.
Though devices and methods for treating benign prostatic hyperplasia have evolved dramatically in recent years, significant improvements have not occurred and such progress is badly needed. As recently as 1983, medical textbooks recommended surgery for removing impinging prostatic tissues and four different surgical techniques were utilized. Suprapubic prostatectomy was a recommended method of removing the prostate tissue through an abdominal would. Significant blood loss and the concomitant hazards of any major surgical procedure were possible with this approach.
Perineal prostatectomy was an alternatively recommended surgical procedure which involved gland removal through an incision n the perineum. Infection, incontinence, impotence or rectal injury were more likely with this method than with alternative surgical procedures.
Transurethral resection of the prostate gland has been another recommended method of treating benign prostatic hyperplasia. This method required inserting a rigid tube into the urethra. A loop of wire connected with electrical current was rotated in the tube to remove shavings of the prostate at the bladder orifice. In this way, no incision was needed. However, strictures were more frequent and repeat operations were sometimes necessary.
The other recommended surgical technique for treatment of benign prostatic hyperplasia was retropubic prostatectomy. This required a lower abdominal incision through which the prostate gland was removed. Blood loss was more easily controlled with this method, but inflammation of the pubic bone was more likely.
With the above surgical techniques, the medical textbooks noted the vascularity of the hyperplastic prostate gland and the corresponding dangers of substantial blood loss and shock. Careful medical attention was necessary following these medical procedures.
The problems previously described led medical researchers to develop alternative methods for treating benign pro static hyperplasia. Researchers began to incorporate heat sources in. Foley catheters after discovering that enlarged mammalian tissues responded favorably to increased temperatures. Examples of devices directed to treatment of prostate tissue include U.S. Pat. No. 4,662,383 (Harada). U.S. Pat. No. 4,967,765 (Turner), U.S. Pat. No. 4,662,383 (Sogawa) and German Patent No. DE 2407559 C3 (Dreyer). Though these references disclosed structure which embodied improvements over the surgical techniques, significant problems still remained unsolved. Recent research has indicated that enlarged prostate glands are most effectively treated with higher temperatures than previously thought. Complete utilization of this discovery has been tempered by difficulties in shielding rectal wall tissues and other nontarget tissues. While shielding has been addressed in some hyperthermia prior art devices, the higher energy field intensities associated with thermotherapy necessitate structures having further capabilities beyond those suitable for hyperthermia. For example, the symmetrical microwave-based devices disclosed in the above-referenced patents have generally produced relatively uniform cylindrical energy fields. Even at the lower energy field intensities encountered in hyperthermia treatment, unacceptably high rectal wall temperatures have limited treatment periods and effectiveness. Further while shielding using radioreflective fluids has been disclosed in the prior art (see for example European Patent Application No. 89,403,199) the location of such radioreflective fluid appears to increase energy field intensity at the bladder and rectal wall. This is contrary to one of the objects of the present invention.
In addition, efficient and selective cooling of the devices is rarely provided. This increases patient discomfort and increases the likelihood of healthy tissue damage. These problems have necessitated complex and expensive temperature monitoring systems along the urethral wall.
Finally, the symmetrical designs of the above-referenced devices do not allow matching of the energy field to the shape of the abnormally enlarged prostate gland. Ideally, the energy field reaching the tissues should be asymmetric and generally should expose the upper and lateral (side) impinging lobes of the prostate gland to the highest energy. In addition, the field is ideally substantially elliptical such that the energy reaching the sphincters is minimized.